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Hydrogen Ions and Acidity

Hydrogen Ions and Acidity. Chapter 19.2. What is K w ?. K w is the equilibrium constant for the self-ionization of water Water molecules are in constant motion and can collide to create a hydronium ion and a hydroxide ion. Where does K w come from?. 2H 2 O (l)  H 3 O + (aq) + OH - (aq)

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Hydrogen Ions and Acidity

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  1. Hydrogen Ions and Acidity Chapter 19.2

  2. What is Kw? • Kw is the equilibrium constant for the self-ionization of water • Water molecules are in constant motion and can collide to create a hydronium ion and a hydroxide ion

  3. Where does Kw come from? 2H2O(l) H3O+(aq) + OH-(aq) Kw = [H+][OH-] __________ [H2O]2 But we remove liquids and solids Kw = [H+][OH-]

  4. Self Ionization ConcentrationIon-Product Constant • Called the self-ionization of water • [H+] = [OH-] = 1.0 x 10-7 M • The ion-product constant for water (Kw) Kw = [H+][OH-] = 1.0 x 10-14 M2 • Neutral solution [H+]=[OH-] • Acidic solution [H+] > [OH-] • Basic solution [H+] < [OH-]

  5. pH Scale and Formulas • pH is an easier way to express the strengths of acids and bases • pH scale ranges from 0-14 0-6 considered acidic RED 7 considered neutral 8-14 considered basic BLUE • pH = -log [H+] [H+] = antilog(pH) • pOH = -log [OH-] [OH-] = antilog(pOH) • pH + pOH = 14 [H+][OH-] = 1.0 x 10-14

  6. Practice Problems • What is the pH of a substance that has an [H+] concentration of 1 x 10-4? What about 1 x 10-5? • What is the pH of a substance that has an [H+] concentration of 6.27 x 10-5? • 4.0; 5.0; 4.2

  7. Practice Problems • What is the [H+] concentration of a substance that has a pH of 8.00? What is the [OH-] concentration? • What is the [H+] concentration of a substance that has a pH of 8.73? What is the [OH-] concentration? What is the pOH? • 1 x 10-8;1 x 10-6;1.86 x 10-9;5.39 x 10-6; 5.27

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